Detersive systems have been used for many years in many cleaning environments including the laundry, warewashing, hard surface cleaning, and other applications. Typically, detersive systems are concentrates comprising mixtures of cleaning ingredients that when mixed with water form a cleaning medium or use composition. Service water, containing some concentration of hardness ions, supplied by local water utilities is most commonly used in making the use composition. Hardness ions are typically undesirable in conjunction with detersive systems since they interfere in the soil removal mechanism. The quality of service water varies from place to place throughout the country and can vary in the amount of hardness and can vary in the type of hardness components. Hardness typically comprises metal ions including calcium, magnesium, iron, manganese, and other typically divalent or trivalent metal cations, depending on the source of the water. The presence of hardness cations in service water can substantially reduce the detersive action or effectiveness of a detersive system, can result in the incomplete cleaning of laundry, dishware, hard surfaces, and other soiled items or surfaces and can leave films or scale comprising the hardness cation and/or components of the detersive system.
A great deal of attention in recent years has been given to the components of detersive systems that reduce the effects of the hardness components. Common hardness sequestering agents comprise inorganic chemicals such as a condensed phosphate compound and a zeolite, and organic sequestrants such as EDTA, organic phosphonates and organic phosphinates. Such agents are effective in treating hardness in service water by a chemical reaction which keeps the ions in the aqueous bulk detersive system but reduces the hardness effect of the ions on the detersive systems. These agents can be effective but can result in both economic and ecological disadvantages.
Recently, softening agents have been prepared for hardness treating or water softening. Such liquid agents can be used in detersive systems at low concentration and can effectively soften service water through a mechanism of removing hardness ions from aqueous media used in detersive systems with little adverse environmental impact or compatibility problems in detersive systems. Such systems work through an organic phase, containing a complexing agent, dispersed in the bulk aqueous phase or aqueous detersive system. The organic phase contains an internal dispersed acid aqueous phase. Hardness ions in the bulk aqueous phase are transferred to the internal acidic aqueous phase through the organic phase by the complexing agent. The driving force of the softening effect is caused by the chemical potential difference in hydrogen ion activity between the inner acidic aqueous phase and the bulk aqueous solution.
We have discovered a novel liquid membrane softening agent that does not contain acid in its internal aqueous phase and thus decreases the potential for corrosion to metals or alloys with which the non-acidic liquid membrane softening agent comes into contact. This reduction in corrosivity will allow for much less costly equipment in both the manufacturing of the softening agent and the detersive system. The use of the softening agent of the invention also result in the benefit of less potential for corrosion at the washing process site. Another possible benefit of this new liquid softening agent is the increased stability of any active chlorine sources which may be included in the detersive systems in which the softening agents maybe included. The liquid membrane softening agent is also advantageous in that a wider variety of organic solvents, surfactants, and complexing agents rather than just acid stable organic solvents, surfactants, and complexing agents can be used in the softening agent resulting in the possibility of a more cost effective softening agent.